Convert Web.Config to a hashtable. Use Keys to get the values.

webconfig hash

<#
web.config.xml

<configuration>
  <applicationSettings>
	<add key="machineName" value="Prod" />
	<add key="anotherMachineName" value="Test" />
	<add key="EnvTypeDefault" value="Dev" />
	<add key="RootURLProd" value="http://domain.com/app/" />
	<add key="RootURLTest" value="http://test.domain.com/app/" />
	<add key="RootURLDev" value="http://localhost/app/" />
	<add key="HumanReadableEnvTypeProd" value="" />
	<add key="HumanReadableEnvTypeTest" value="Test Mode" />
	<add key="HumanReadableEnvTypeDev" value="Development Mode" />
	</applicationSettings>
</configuration>
#>

[xml]$webconf = Get-Content 'web.config.xml'
$x = $webconf.configuration.applicationSettings.add
$hash = @{}
foreach ($y in $x) {
$hash.Add($y.key,$y.Value)
}
$hash.machineName